Magnesium radicals MgC${}_5$N and MgC${}_6$H in IRC+10216

Abstract

After the previous discovery of MgC${}_3$N and MgC${}_4$H in IRC+10216, a deeper Q-band (31.0-50.3 GHz) integration on this source had revealed two additional series of harmonically related doublets that we assigned on the basis of quantum mechanical calculations to the larger radicals MgC${}_5$N and MgC${}_6$H. The results presented here extend and confirm previous results on magnesium-bearing molecules in IRC\,+10216. We derived column densities of (4.7$\pm$1.3)$\times$10${}^{12}$ for MgC${}_5$N and (2.0$\pm$0.9)$\times$10${}^{13}$ for MgC${}_6$H, which imply that MgC${}_5$N/MgC${}_3$N=0.5 and MgC${}_6$H/MgC${}_4$H = 0.9. Therefore, MgC${}_5$N and MgC${}_6$H are present with column densities not so different from those of the immediately shorter analogs. The synthesis of these large magnesium cyanides and acetylides in IRC+10216 can be explained for their shorter counterparts by a two-step process initiated by the radiative association of Mg${}^{+}$ with large cyanopolyynes and polyynes, which are still quite abundant in this source, followed by the dissociative recombination of the ionic complexes.

5 pages, 3 figures

References in corpus (4)

• Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene and indene
• New molecules in IRC+10216: confirmation of C${}_5$S and tentative identification of MgCCH, NCCP, and SiH${}_3$CN
• Yebes 40 m radio telescope and the broad band NANOCOSMOS receivers at 7 mm and 3 mm for line surveys
• Discovery of the first Ca-bearing molecule in space: CaNC

Cited by in corpus (13)

• Carbon-Chain Chemistry in the Interstellar Medium
• Discovery of the elusive thioketenylium, HCCS+, in TMC-1
• The magnesium paradigm in IRC+10216: Discovery of MgC${}_4$H${}^{+}$, MgC${}_3$N${}^{+}$, MgC${}_6$H${}^{+}$, and MgC${}_5$N${}^{+}$
• Laboratory and astronomical discovery of magnesium dicarbide, MgC${}_2$
• Ultra-deep 31.0-50.3 GHz spectral survey of IRC+10216
• Discovery of a new molecular ion, HC7NH+, in TMC-1
• Discovery of two metallic cyanoacetylides in IRC+10216: HMgCCCN and NaCCCN
• Molecules in the carbon-rich protoplanetary nebula CRL 2688
• Laboratory observation and astronomical search of 1-cyano propargyl radical, HCCCHCN
• CN and CCH derivatives of ethylene and ethane: Confirmation of the detection of CH${}_3$CH${}_2$CCH in TMC-1
• Detection of the linear SiC${}_3$ and SiC${}_5$ radicals in IRC\,+10216
• A high-resolution spectroscopic analysis of aminoacrylonitrile and an interstellar search towards G+0.693
• Development of a glow-discharge ion-trap instrument for measuring effective radiative-association rate coefficients